Revert "Address the poor performance of the existing unique-name generation (#17944)"

This reverts commit 83202d8ad6.

# Conflicts:
#	src/Base/Tools.cpp
#	src/Base/Tools.h

src/Base/Writer.cpp

@@ -247,19 +247,56 @@ std::string Writer::addFile(const char* Name, const Base::Persistence* Object)
     assert(!isForceXML());
 
     FileEntry temp;
-    temp.FileName = Name ? Name : "";
-    if (FileNameManager.containsName(temp.FileName)) {
-        temp.FileName = FileNameManager.makeUniqueName(temp.FileName);
-    }
+    temp.FileName = getUniqueFileName(Name);
     temp.Object = Object;
 
     FileList.push_back(temp);
-    FileNameManager.addExactName(temp.FileName);
+
+    FileNames.push_back(temp.FileName);
 
     // return the unique file name
     return temp.FileName;
 }
 
+std::string Writer::getUniqueFileName(const char* Name)
+{
+    // name in use?
+    std::string CleanName = (Name ? Name : "");
+    std::vector<std::string>::const_iterator pos;
+    pos = find(FileNames.begin(), FileNames.end(), CleanName);
+
+    if (pos == FileNames.end()) {
+        // if not, name is OK
+        return CleanName;
+    }
+
+    std::vector<std::string> names;
+    names.reserve(FileNames.size());
+    FileInfo fi(CleanName);
+    CleanName = fi.fileNamePure();
+    std::string ext = fi.extension();
+    for (pos = FileNames.begin(); pos != FileNames.end(); ++pos) {
+        fi.setFile(*pos);
+        std::string FileName = fi.fileNamePure();
+        if (fi.extension() == ext) {
+            names.push_back(FileName);
+        }
+    }
+
+    std::stringstream str;
+    str << Base::Tools::getUniqueName(CleanName, names);
+    if (!ext.empty()) {
+        str << "." << ext;
+    }
+
+    return str.str();
+}
+
+const std::vector<std::string>& Writer::getFilenames() const
+{
+    return FileNames;
+}
+
 void Writer::incInd()
 {
     if (indent < 1020) {